A waveguide power divider used in a feed circuit of an array antenna is preferably able to set its power distribution ratio to an arbitrary ratio. For example, as a conventional waveguide power divider meeting this demand, the invention described in Patent Document 1 is known.
That is, the conventional waveguide power divider capable of setting a power distribution ratio to an arbitrary ratio is configured such that a first rectangular waveguide and a second rectangular waveguide are arranged by stacking in parallel, both waveguides are connected by a coupling window of which longitudinal direction is orthogonal with a tube axis, and that a short thin-wall portion is provided in the second rectangular waveguide.
The conventional waveguide power divider can set a power distribution ratio to an arbitrary ratio by displacing a center of the coupling window from a center of the thin-wall portion.
Patent Document 1: Japanese Patent Application Laid-open No. 2005-159767 (FIGS. 6 and 7)